Simultaneous dual extraction of light and heavy aromatic hydrocarbons from hydrocarbon mixtures



Nov. 10, 1970 A. I... BENI-IAM .ETAL 3,539,503

SIMULTANEOUS DUAL EXTRACTION OF LIGHT AND HEAVY AROMATIC HYDROCARBONS FROM HYDROCARBON MIXTURES Filed Aug. 19, 1968 3 Sheets-Sheet 1 LIGHT PARAFFINS 73.9 Ib/hr, LIGHT ARoMATIC zal Ib/hr.

D: DE 3 E 21 WATER 9 O E 42 I '5 U I 0I 0i 0I D: I S LI. i E z 46 N 'l o :k

-II'I v HEAVY ARoMATIc t 8g lHEAvY PARAI-'EIN 33am/hr. 52 5 E 54 48.4Ib/m.

E m g MIXER g E MIXER T (D Is S 2o WATER f E 3 t wATER 22 9, 24

#I FEED IooIb/nr.

#I ExTRAcToR #2 ExTRAcToR #2 ExTRAcT #I ExTRAcT FIG. lv

ALVIN L. BENHAM MARK A. PLUMMER LES ORTON Nov. 10, 1970 A, L, BENHAM ETAL 3,539,503

SIMULTANEOUS DUAL EXTRACTION OF LIGHT AND HEAVY AROMATIC HYDROCARBONS FROM HYDROCARBON MIXTURES Filed Aug. 19, 1968 3` Sheets-Sheet 2 LIGHT PARAFFIN 62.6 Ib/hr. UGHT AR0MAT|C 37,4|b/hr 56 l l 58 E A E g i wATER 9 o '5 f 42 5 I E E E, 'Q u. 4E 'E 'is N 3 gg o 46 :H: HEAVY ARoMATnc l im 8g t HEAVY PARAFFIN I0 32.6 lb/hr. 52 54 H44 lb/hr.

3 Lu (D E f E MlxER g E LL I- u. '8 t; 5 E Di (I WATER f n.. J N

#l FEED oom/hr.

#2 ExTRAcToR i 8 4 #l ExTRAcToR #2 EXTRACT #l ExTRAcT FIG. 2

/N VEN TRS ALVIN L. BENHAM MARK A. PLUMMER NORTON rHY Nov. l0, 1970 A. L. BENI-IAM ETAL 3,539,503

SIMULTANEOUS DUAL EXTRACTION OF LIGHT AND HEAVY AROMATIC HYDROCARBONS` FROM HYDROCARBON MIXTURES Filed Aug. 19, 1968 5 Sheets-Sheet 3 LIGHT PARAFFIN 63.5 Ib/hr. LIGHT AROMATIC 36.5 Ib/hr.

0: O E 9 WATER 9 O S :t 42 In I n: q n: n: o I l Ii *"2 L 44 2z 46 N #t s E9 o *t .J|

HEAVY AROMATIC P gg HEAVY PARAFFIN 25.4 Ib/hr. 52 sETTLI-:R 54 IO4.6 Ib/hr.

30 26 a h. 4 .C m L MIXER A 'i l '8 i '.5 w D: WATER 5 #N #IFEED loom/nr. m*

#2 FEED |30 lb/hr.

#l ExTRAcToR #2 ExTRAcToR #2 ExTRAcT #l ExTRAcT 57o lb/hr,

FIG. 3

INVENTORS ALVIN L. BENHAM MARK A. PLUMMER A T TOR United States Patent O 3,539,503 SIMULTANEOUS DUAL EXTRACTION OF LIGHT AND HEAVY AROMATIC HYDROCARBONS FROM HYDROCARBON MIXTURES Alvin L. Benham, Findlay, Ohio, and Mark A. Plummer,

Littleton, and Charles J. Norton, Denver, Colo., assignors to Marathon Oil Company, Findlay, Ohio, a corporation of Ohio Filed Aug. 19, 1968, Ser. No. 753,540 Int. Cl. Cg 21/00, 21/12 U.S. Cl. 208-317 7 Claims ABSTRACT OF THE DISCLOSURE CROSS REFERENCES TO RELATED APPLICATIONS U.S. patent application Ser. No. 674,687, A. L. Benham, tiled Aug. 30, 1967, now Pat. No. 3,415,743 and assigned to Marathon Oil Company, Findlay, Ohio, generally relates to the iield of the present invention inasmuch as it teaches the use of two extraction zones to extract aromatic compounds from mixtures with nonaromatic compounds with a selective solvent.

No related U.S. patents, or applications, are known to the inventors which disclose a simultaneous, dual extraction process using a continuous recycling of a selec tive solvent to extract aromatics from two separate feeds in order to obtain tour product streams.

BACKGROUND OF THE INVENTION Field of the invention The invention teaches an improvement in hydrocarbon purification; U.S. patent class 208, Mineral Oils: Processes and Products, contains art generally pertinent to same.

Description of the prior art U.S. Pat. 2,928,788 to Jezl teaches an extractive process wherein lubricating oil, from which mononuclear and polynuclear aromatic hydrocarbons have been removed, is contacted with a selective solvent such as furfural in order to obtain high viscosity index raitinates.

U.S. Pat. 3,168,463 to Norton et al. describes the extraction of aromatic hydrocarbons from a mixture of aromatic hydrocarbons with non-aromatic hydrocarbons by treating a mixture of said hydrocarbons with a selective solvent consisting of an intimate mixture of furfural, furfural alcohol, and Water.

U.S. Pat. 2,201,549 to Van Dijck discloses a process for extracting two or more liquid mixtures with a selective solvent but the crucial process variables for the commercial extraction of aromatics from hydrocarbon feed streams is not taught therein. A

British Pat. 829,432 to Bankowski, Kothnig and Klemt claims a process for the separation of aromatic hydrocarbons from hydrocarbon mixtures by means of two extraction operations using a primary and a secondary solvent.

U.S. Pat. 3,317,422 to Benham teaches the closedloop multiple extraction of aromatic hydrocarbons from hydrocarbon mixtures using a common selective solvent.

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SUMMARY (l) General statement of the z'fzvent01z.-For the rst time, this process simultaneously extracts aromatics using a continuous recycling selective solvent for such extraction, from two distinct hydrocarbon feed mixtures: a light aromatic, light paraiiinic stream; and, a heavy aromatic, heavy paraflinic stream, in order to obtain four separate product streams: a light aromatic product stream, a heavy aromatic product stream, a light parafinic product stream, and a heavy paraftinic product stream. The terms light and heavy as used herein refer to specific boiling ranges; light species a lower boiling range encompassed by about F. to about 400 F., and heavy species a higher boiling range from about 400 F. to about 700 F.

(2) Utility of the inve1ztio1z.-This invention permits a flexibility of refining operation formerly unknown to the art. The economic advantages which will occur in terms of capital investment and operating expense are readily apparent.

DESCRIPTION OF THE DRAWINGS FIGS. 1, 2, and 3 are schematic How sheets of embodiments of the invention.

Referring now to FIG. 1, the solvent used consists of 45% by volume dimethylformamide, 45 by volume tetramethylene sulfone, and 10% water by volume. The ratio of number 1 extract to number 1 feed is 2.6 volumes per volume. The ratio of the number 2 feed to the number 1 feed is 0.72 volume per volume.

In FIG. l, the number 1 feed stock, 100 lbs/hr. of reformate comprising a mixture of light aromatic-light parainic hydrocarbons is introduced into extractor 4 through line 2. The number 2 feed stock, 81.7 lbs/hr. of a light catalytic cycle oil, comprising a mixture of heavy aromatic and heavy paratiinic hydrocarbons is introduced into extractor 8 through line 6. The number 1 extract from extractor 4, consisting essentially of a mixture of the solvent and light aromatics, is recycled to extractor 8 through line 10. The number 2 extract from extractor 8, consisting essentially of the solvent and heavy aromatics, is recycled to extractor 4 through line 12. A raffinate stream consisting essentially of light paraiiins, heavy aromatics and a small amount of solvent (less than 10% by volume) is withdrawn from extractor 4 through line 14, and introduced into mixer 18, which is supplied with Water from line 22. A second raiiinate stream consisting essentially of heavy paraflins, light aromatics and a small amount of solvent is withdrawn from extractor 8 through line 16 and introduced into mixer 20, which is provided with water from line 24. The raffinate stream from extractor 4 is then removed, line 26, to settler 30. The rafiinate stream from extractor 8 is introduced into settler 32 via line 28. The solvent, and Water, are removed from the raffinate streams in settlers 30 and 32 through lines 34 and 36. On line 38, the solvent and water from lines 34 and 36 are introduced into solvent fractonator 40 from which water is withdrawn overhead, line 42, and the solvent is removed as bottoms, line 37, to mix with the extract from extractor 4 which is recycled to extractor 8 through line 10.

The raffinate stream from extractor 4 is removed from settler 30 through line 44 and introduced into fractionator 48, from which the heavy aromatics, 33.3 lbs/hr. are removed as bottoms, line 52, and the light paraflins, 73.9 lbs/hr. are removed overhead, line 56. The rainate stream from extractor 8 is removed from settler 32 through line 46 and introduced into fractionator 50, from which the heavy paraflins 48.4 lbs/hr. are removed as bottoms, line 54, and the light aromatics, 26.1 lbs/hr., are removed overhead, line 58.

Turning now to FIG. 2, the solvent used is 90% by volume tetramethylene sulfone and by volume water. The ratio of the number 1l extract to the number 1 feed is 5.0 volumes per volume. The ratio of the number 2 feed to the number 1 feed is 1.3 volumes per volume. The rst feed charge, reformate comprising a mixture of light aromatics and light parains, 100 lbs/hr., is introduced into extractor 4 through line 2. The second feed stock, a light catalytic cycle oil comprising a mixture of heavy aromatics and heavy parans, 147 lbs./hr., is introduced into extractor 8 through line 6. The number 1 extract from extractor 4 consisting essentially of the solvent and light aromatics, is recycled to extractor 8 through line 10. The number 2 extract from extractor 8, consisting essentially of the solvent and heavy aromatics, is recycled to extractor 4 through line 12. The railinate stream from extractor 4 consisting essentially of light parans and heavy aromatics, and a small amount of solvent, is introduced through line 14 into mixer 18, which is supplied with water from line 22. The raftinate stream from extractor 8, consisting essentially of heavy parans, light aromatics and a small amount of solvent, is introduced via line 16 into mixer 20, which is provided with water from line 24. The rafnate stream from extractor 4 is then introduced through line 26 into settler 30, from which the solvent and the water are removed through line 34. The raffinate stream from extractor 8 is removed by line 28 to settler 32, from which the solvent and water are withdrawn via line 36. `On line 38, the solvent and water removed through lines 34 and 36 from settlers 30 and 32 are introduced into solvent fractionator 40, from which water is removed overhead, line 42. At the bottom of solvent fractionator 40, the solvent is removed, line 37, to mix with the number 1 extract from extractor 4 which is recycled to extractor 8 through line 10.

The raffinate stream from extractor 4 is removed, line 44, from settler 30 and introduced into fractionator 48 from which 32.6 lbs./hr. of heavy aromatics are removed as bottoms, line 52, and 62.6 lbs./hr. light parati-ins are removed overhead, line 56. The raflinate stream from extractor 8 is removed from settler 32, line 46, and introduced into fractionator 50, from which 114.4 lbs./hr. heavy parains are removed as bottoms, line 54, and 37.4 lbs/hr. light aromatics, are removed overhead, line 58.

In FIG. 3, the solvent used is 80% by volume dimethylformamide and by volume Water. The ratio of the number 1 extract to the number 1 feed is 4.6 volumes per volume. The ratio of the number 2 feed to the number 1 feed is 1.1 volumes per volume. The number 1 feed, 100 lbs/hr., comprising a reformate mixture of light aromatic-light parafnic hydrocarbons, is introduced via line 2 into extractor 4. The number 2 feed, 130 lbs/hr., comprising a cycle oil containing heavy aromatic-heavy paraffinic hydrocarbons, is introduced on line 6 into extractor 8. The extract from extractor 4, consisting mostly of the solvent and light aromatics, is recycled to extractor 8 through line 10. The extract from extractor 8, consisting mostly of the solvent and heavy aromatics, is recycled to extractor 4 through line 12. The number 1 ra'inate stream, consisting essentially of light parans, heavy aromatics and a small amount of solvent, is removed from extractor 4, line 14, and introduced into mixer 18, which is supplied with water from line 22. The number 2 railnate stream, consisting essentially of heavy parans, light aromatics and a small amount of solvent, is removed from extractor 8, line 16, and introduced into mixer 20, which is supplied with water from line 24. The number 1 ranate stream is removed from mixer 18, line 26, and introduced into settler 30, from which water and the solvent are withdrawn, line 34. The second raffinate stream is removed from mixer 20, line 28, and introduced into settler 32, from which water and the solvent are removed on line 36. The water and solvent from lines 34 and 36 are introduced, line 38, into solvent fractionator 40, from which water is withdrawn overhead, line 42. The solvent is removed as bottoms via line 37 to mix with the rst extract from extractor 4, line 10, which is recycled to extractor 8.

The number 1 raffinate stream from extractor 4 is removed from settler 30 on line 44 and introduced into fractionator 48, from which 25.4 lbs./ hr. heavy aromatics are removed as bottoms, line 52, and 63.5 lbs/hr. light parans are removed overhead, line 56. The number 2 raffinate stream from extractor 8 is removed from settler 32 on line 46 and introduced into fractionator 50, from which 104.6 lbs/hr. heavy parafns are removed through line 54, as bottoms, and 36.5 lbs./ hr. light aromatics are removed through line 58, overhead.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (l) Starting materials-Reformed naphthas, known to the art as reformate, are appropriate as the number 1 feed stock for this invention. Reformate preferably contains from C6 to C10 hydrocarbons, both aromatics and non-aromatics. In the claims appended hereto reformate is characterized as the light aromatic-light parainic mixture.

The September 1966, edition of Hydrocarbon Processing at page 200, lists the following as some typical properties of reformate: gravity API 47.7; I.B.P. 114 F.; D.P. 406 F.; research octane number, clear, 89.5; composition based on volume percentage, parafns, 39.1%; olefns, 1.1%; naphthenes, 3.4%; and aromatics, 56.4%.

Reformate boiling in the range of about F. to about 400 F. is suitable feed material for the invention, but reformates boiling at 100 F. to about 350 F. are preferable, and reformate boiling at F. to about 320 F. is most preferable.

Turning to the drawings, in FIG. 1 reformate boiling between about 100 F. to about 400 F. was employed as the number 1 feed; in FIG. 2, reformate mixtures boiling in the range of 100 F. to about 350 F. formed the number 1 feed stock; and, a 100 F. to about 350 F. reformate was used as the number 1 feed in FIG. 3.

Hydrocarbon feed stocks suitable for use as the second feed stock may be formed from light catalytic cycle oils, sometimes called cycle oils, which are about 400 F. to about 700 F. distillation fractions produced from the catalytic cracking of petroleum. They comprise a heavy aromatic-heavy parafnic mixture. No one set of characteristics will describe light catalytic cycle oils since petroleum does vary in its composition. However, W. L. Nelson, Petroleum Refining and Engineering, 3rd Ed., McGraw-Hill Co., Inc. (1949), 830 pages, explains on page 674 some general properties of these distillation fractions. -Properties mentioned there comprise: gravity, 20 to 30; characterization factor, 10.6 to 11.6 or lower; boiling range, 400 F. to 650 F. Also, C. Brown et al., Cycle Stocks From Catalytic Cracking, Industrial and Engineering Chemistry, vol. 38, p. 136A (1946), gives the characteristics of several light catalytic cycle oils from different petroleum bases.

Light catalytic cycle oils (LCCOs) boiling from 400 F. to about 700 F. comprise the Ibroad range of hydrocarbons operable with the invention. They are described herein as the number 2 feed.

(2) Process variables.-The ratios of the number 1 extract rate to the number 1 feed rate, and the ratios of the number 2 feed to the number 1l feed, are significant process variables herein. An operable ratio of the number 1 extract rate to the number 1 feed rate is about 0.5 to about 8.0 volumes per volume. Preferably, the ratio should be 1 to about 6 volumes per volume, and most preferably the ratio should be 2 to about 4 volumes per volume.

The ratio of the number 2 feed to the number 1 feed in this invention must 'be at least 0.15 to about 6 volumes per volume. A preferred ratio would be 0.25 to about 3 volumes per volume; most preferably, the ratio of number 2 feed to the number 1 feed should be 1 to about 2 volumes per volume.

Temperature is an important variable. Broadly speaking, extraction temperatures between about 40 F. to about 150 F. are operable but temperatures between 50 F. to about 100 F. are preferable, and temperatures in the range of ambient to about 90 F. are most preferable.

Fractionator temperatures will be conventionally determined by the feed materials utilized and the products desired.

Pressures are not narrowly critical to this invention but they should be of such a nature that they permit the process to operate in a continuous liquid state. Vacuum, super atmospheric or steam distillation can be utilized if desired.

(3) SOZvents.-In an extraction process the nature and the character of the particular solvents used are essential to the ethciency of the process. In this invention, appropriate solvents must have a high capacity for both light aromatics and heavy aromatics, and a low capacity for light paraftins and heavy paraiiins when they are mixed with the two suitable feed streams. Furthermore, operable solvents must contain from about 1% to about 30% by volume of water. Preferably, the range of water content in the solvents should be from about 2% to about 20% by volume, and most preferably the water content should be about 10% by volume.

`Suitable solvents comprises mixtures of tetramethylene sulfone, dimethylformamide, and water. Preferably, solvent compositions should include amounts of dimethylformamide from to about 99% by volume; and amounts of tetramethylene sulfone from 0% to about 99% by volume. More preferably, amounts of dimethylformamide and tetramethylene sulfone should range from about to about 50% by Volume, and most preferably dimetyhlformamide should be about 65% by volume, and tetramethylene sulfone about by volume. The above mixtures are considered preferable, especially when using typical LCCO and reformate feeds in equal quantities, each feed stream containing about 5% to about 75% aromatics. Other combinations of tetramethylene sulphone, dimethylformamide and water can be used so that optimum yields and purities of the two aromatic streams are obtained.

Solvents must be removable from the rafnate streams by any suitable methods known to the art, as for example, by water washing.

This invention is capable of a variety of modifications and variations which will be made apparent to those skilled in the art by a reading of this specification, and which are to be included within the spirit of the claims appended hereto.

What is claimed is:

1. A simultaneous, dual extraction process utilizing two separate hydrocarbon feeds, one of said feeds consisting essentially of a mixture of light aromatic hydrocarbons with light paraffin hydrocarbons, and the other of said feeds consisting essentially of a mixture of heavy aromatic hydrocarbons with heavy paraffin hydrocarbons, said eX- traction process yielding as product streams, a light aromatic product stream, a heavy aromatic product stream, a light paraflinic product stream, and a heavy paraiinic product stream; said process comprising in combination the steps of:

(a) feeding to a first extractor said light aromatic-light parainic mixture,

(b) feeding to said lirst extractor a mixture of a solvent comprising dimethylformamide, tetramethylene sulfone and from l to about 30% by volume of water containing heavy aromatic hydrocarbons, having a high capacity for both said light aromatics and said heavy aromatics and having a low capacity for said light paraiiins and said heavy paraffins,

(c) withdrawing from said first extractor an extract consisting essentially of a mixture of said solvent with at least a portion of said light aromatics,

(d) withdrawing from said iirst extractor a raflinate stream consisting essentially of light paraffins, heavy aromatics and a small amount of solvent,

(e) feeding said extract stream from said first extractor into a second extractor,

(f) feeding to said second extractor said heavy aromatic-heavy parainic mixture,

(g) withdrawing from said second extractor a second extract stream consisting essentially of said solvent and at least a portion of said heavy aromatics,

(h) withdrawing from said second extractor a second raiiinate stream consisting essentially of said heavy parafiins, said light aromatics and a small amount of solvent,

(i) feeding said second extract stream consisting of the solvent and at least a portion of said heavy aromatics, to said first extractor,

(j) removing any entrained solvent from said first rainate stream,

(k) removing any entrained solvent from said second raffinate stream,

(l) distilling said first raflinate stream to separate said light paraflins from said heavy aromatics,

(m) distilling the second raffinate stream to separate said heavy parans from said light aromatics.

2. The process of claim 1 wherein the solvent is removed from said rafnates by water-washing.

3. The process of claim 1 wherein the solvent consists essentially of dimethylformamide, tetramethylene sulfone, and from about 1 to about 30% by volume of water.

4. The process of claim 1 wherein the ratio of the number 1 extract rate to the number 1 feed rate is about 0.5 to about 8 volumes per volume.

5. The process of claim 1 wherein the ratio of the number 2 feed to the number 1 feed is about 0.15 to about 6 volumes per volume.

6. The process of claim 1 wherein the extraction temperature for said process is in the range of about 40 F. to about 150 F.

7. The process of claim 1 wherein the two hydrocarbon feed streams comprise reformate containing hydrocarbons boiling in the range of about F. to about 400 F. as the number 1 feed, and light catalytic cycle oils boiling in the range of about 400 F. to about 700 F. as the number 2 feed.

References Cited UNITED STATES PATENTS 2,201,549 5/1940 Van Dijck 208-317 2,201,550 5/1940 Van Dijck et al. 208-317 2,270,827 1/1942 Tijmstra 208-317 3,415,743 12/1968 Benham 208-317 3,461,066 8/1969 Morris et al 208-321 L) HERBERT LEVINE, Primary Examiner U.S. Cl. X.R. 

